TDSOJohn

joined 2 years ago
[–] TDSOJohn@lemmy.world -2 points 2 months ago (2 children)

Thanks for the info, seems to be the case πŸ˜… will definitely refrain from commenting more here

[–] TDSOJohn@lemmy.world 3 points 2 months ago

I don’t think the main target is civilians, I think they have better targets (strategically speaking), you are right in this

[–] TDSOJohn@lemmy.world -2 points 2 months ago (1 children)

Badass bro. Nothing screams β€œI don’t care” like posting this πŸ˜‚πŸ˜‚

[–] TDSOJohn@lemmy.world -4 points 2 months ago (5 children)

Is it the place where people stop using their brains? O.O sorry first time here lol

[–] TDSOJohn@lemmy.world 2 points 2 months ago (31 children)

They killed civilians. I have a friend who has a relative killed.

[–] TDSOJohn@lemmy.world -2 points 2 months ago (1 children)

Justifications? Every kill is bad wtf are u even talking about πŸ˜‚πŸ˜‚πŸ˜‚

[–] TDSOJohn@lemmy.world 1 points 3 months ago (1 children)

Thanks for the detailed answer! We're doing a constant current source. The circuit you have linked would be perfect for future designs, but could a PMOS-FET be a drop-in replacement if we were to reuse the current PCBs we have? Do you have any suggestions on a specific model.

[–] TDSOJohn@lemmy.world 2 points 3 months ago (2 children)

Low side switching is not an option unfortunately. Are the N-fets a solution to the transistor voltage drop?

Also, do you think we should be looking for a replacement for the LM317 for future designs?

[–] TDSOJohn@lemmy.world 2 points 3 months ago

Thanks. J5 is 6 parallel jumpers to probe and adjust the current via RV[1-6]. J6 is connected to the laser diodes. As explained in another answer, we unfortunately must use a common ground.

[–] TDSOJohn@lemmy.world 2 points 3 months ago

hi, thanks for the early reply.

the relevant output is j6 which is connectect to six red lasers with separate positive terminals and a common ground to power them independently using the pwm function of arduino. They should be a mostly resistive load but they have quite high parassitic capacitance. We can't have separate grounds and switch low side since the external casing of the lasers is connected to the negative terminal of the laser diode and it is bolted to the same aluminum frame. The lm317 is working as a constant current driver and we found online that it's best to switch Vi instead of ADJ in this case link. Is it possible to use the circuit in the first schematic of the link to solve this? We are currently dropping .7V between base and emitter of the transistors.

Could otherwise placing the switching transistor after the cc driver be a solution?

The circuit seems to work perfectly with a lower voltage laser diode and doesn't seem to have problems with transients. Also thanks, will try to simulate it in spice!

 

Hello everyone, We have a problem with a circuit we built. The circuit seems to work properly with a green laser diode (130mA, lower voltage). With the red laser (higher voltage) on the other hand, the circuit delivers only 60mA max of the 130mA it should be giving the laser.

The problem seems to be the transistor's resistance because it works properly if we bypass the transitor and give +5V to the LM317.

Is it this assumption correct?

We tried a few transistors (BC241, BC236, TIP41C and TIP41) but with no luck. Is there a way to find a drop-in replacement for the transistor? MOSFET seem to have lower resistance but require an external driver with Arduino.

We need to use the Arduino PWM with these drivers, so at least 980hz switching frequency is needed.

Thanks in advance

Link to the schematics

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